use the same color (#EEEEEE) for all empty views and reader
rename and unify grey background name
unify comments, stats and media background color
Detect when the application moves BG to FG and ping the Push Notifications backend
Remove unused code
Fix some style issues, and reset the 'background' variable in mustPingPushNotificationsBackend
Merge branch 'develop' into feature/403-ping-pushnotifications-backend

Conflicts:
	src/org/wordpress/android/WordPress.java
Merge pull request #408 from wordpress-mobile/issue/392-use-same-bg-color-empty-views

Fix #392 - use same bg color empty views
Merge branch 'develop' of https://github.com/wordpress-mobile/WordPress-Android into feature/reader-redesign-post-detail